Method of saturating sheet material



Sept 23, 1930. 1 KIRSCHBRAUN l, 776,590

METHOD OF SATURATING SHEET MATERIAL Fled Sept. 16. 1926 Patented Sept. 23, 1930 UNITED STATES PATENT OFFICE LESTER KIRSCI-IBRAUN, OF LEONIA, -NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE PATENT AND LICENSING CORPORATION, OF BOSTON, MASSACHUSETTS, A.

CORPORATION 0F MASSACHUSETTS METHOD or SATURATING SHEET MATERIEL Application filed September 16, l1926. Serial No. 135,960.`

rl.`his invention relates to amethod of saturating absorbent bodies, such for example as felted sheet material, with liquid or liquefied saturants which expand when heated and contract when cooled. As this property is common to practically all liquidsthe invention essentially relates to the utilization of thermal expansion and contraction to effect more complete and thorough saturation of absorbent bodies, particularly where the saturant isrelatively thick or viscous. My invention finds an application and illustration in the fabricated roofing industry wherein felted fibrous `sheets are saturated or impregnated with a waterproofing compound, such as molten asphalt, pitch, wax or the like. Roofing of this type as commonly made comprises a sheet of felted fibrous material formed on'a paper-making machine of rag or asbestos fiber ormixtures of these with each other or with other kinds of fiber. The felt sheet is impregnated with molten asphalt. For this purpose, a low melting-point asphalt 1s customarily used since the use of a high melting-point asphalt would ordinarily necessitate such a temperature to liquefy it sutliciently to penetrate the sheet as to char and injure the sheet itself. The usual practice therefore is to impregnate the body of the sheet with low melting-point asphalt, remove the excess from the surface, then coat the faces of the she-et with high. melting-point asphalt to provide an impervious layer or facing which will not run under. solar heat.

It is desirable to impregnate the body o1' the sheet as completelyA as possible since not only is its waterproof qualities dependent to some extent on the completeness of the satura- "tion, butthe mechanical strength of the sheet l varies with the amount of saturant absorbed.

mersed in molten asphalt and allowed to re-4 dry in as the felt cools, a considerably larger amount of saturant is absorbed. Further absorption can be obtained by immersing for a relatively shortv period, partially cooling the felt with excess saturant on the surface, then briefly immersing a s'econd tlme,

then allowing excess saturant to dryf in as Y the sheet cools. By choosing suitableperiods for the successive immersions and coolings, Ordinar roofing felt can be made to absorb a quantity of low melting-point asphalt substantially equal toits theoretical capacity, the total time of immersion beingcomparatively brief. The interruption in the saturation which allows an interval of cooling between successive lmmerslons appears to have the effect of causing the saturant and residual f air within the sheet to contract by cooling and thus to draw or suck into the sheet the saturant on the surface thereof. The next immersion by heating the absorbed saturant and residual air, expels practically all of the latter and also provides another surface layer of saturant to be sucked in during the cooling. In this way, the saturation of roofing felt with low melting-point asphalt (150 F.) heatedvto 425 F. or so may be made practically complete. The temperature of any given bath must depend on the characteristics of the saturant used, and should be of such a degree as to roduce the desired fluidity in the saturant. n the manufacture of sheet roofing, however, it is not desirable to have the felt completely filled with low ymelting-point asphalt, since a coating of high "melting-point asphalt on such roofing would be liable to slip under the action of solar heat.

In order to anchor the coating'v to the fibrous structure therefore, I partially saturate the felt with high melting-point asphalt as follows z-After immersing the felt in low melting-point asphalt to Wet the fibers therewith, I remove the excess from the surface and replace it at once with molten, high meltingpoint asphalt and permit an interval of cooling. It is well known that an absorbent body takes up a liquid with far greater facility if the body has previously been wet through with the liquid. Thus the high meltingpoint asphalt which penetrates with difficulty the pores of dry felt, enters more readily if the fibers have been previously wetted with a more liquid asphalt. The contracting saturant sucks in the surface asphalt, and a subsequent immersion in high melting-point asphalt followed by a period of cooling results in a degree of saturation which is close to the theoretical maximum. In this case, the saturant in the pore spaces to a considerable depth from the surface is high melting-point asphalt which will hold the usual coating and slate surfacing without slippage. Roofing elements cut and finished from sheet roofing which has been impregnated according to my invention are stronger and more durable than roofing of the same type now in use, are less liable to deterioration under the action of the weather, and thus will retain their good appearance and weatherproof qualities for a longer time.

To carry out my invention, I have devised a machine for making sheet roofing of superior quality from raw roofing felt. VFor a full understanding of this machine, refer-V ence may be had to the drawing which illustrates conventionally apparatus, the elements of which are well known in the art.

Referring to the drawing in detail, a sheet of rooiing felt 10 is led into a container 11 filled with molten asphalt 12. The asphalt in the `container 11 is preferably of a melting point of approximately 100 to 150, theV bath being maintained at a temperature of approximately 425 F., these temperatures and those indicated on the drawing being by way of example only, and depending on the kind o f asphalt stock used and on the viscosity desired. After the sheet has been immersed for a sufficient period to heat the fibers, convert the moisture into steam, impregnate the felt with the saturant and to wet the fibers thoroughly with saturant, it is then passed through a pair of press rolls 13 which are preferably heated and which remove from the body'and surface of the sheet as much of the low melting-point asphalt as possible. Immediately thereafter and with no appreciable cooling interval while the sheet is substantially at the temperature of the bath l2,

. a coating of high melting-point asphalt is applied to both surfaces thereof as by a suitable spout 14 with a spreading roll 15 and a cooperating coating roll 16 which picks up asphalt from a container 17 directly or by means of a feed roll 18. The asphalt in the container 17 and that supplied through the spout 14 is preferably of approximately 220 melting point. plied at a temperature of between `850 and This asphalt may beep` 450 which is sulicient to maintain it in l liquid form, but which may be lower than the temperature of the sheet at this point. The effect of the temperature on the sheet at this stage is to cool the low melting-point saturant and remaining air within the body of the sheet, causing them to contract and thereby to suck into the sheet the coatings of high melting-point asphalt which have been deposited on the surface thereof. This cooling and sucking-in operation is allowed to proceed while the sheet is carried over suitable looping rolls 19 whereon it is supported in such a way as to be partially cooled by exposure to the atmosphere. The partially cooled sheet is thereupon led into a second container 20 in which is a bath 21 of high melting-point asphalt (e. g., 220 F.), the bath being maintained at approximately 425 F. In passing through this bath, the sheet being cooler than the bath of saturant is again heated through, the effect being to expel lpractically all of the residual air and moisture which have been retained up to this point in some of the pores and voids of the sheet. Upon emerging from the container 20, the sheet is lightly scraped by suitable doctors 22 which are adjusted to remove superiuous coating from the surface, but to leave thereonit is cooled by the atmosphere, after which it may be chilled and rolled up for shipment as a saturated sheet or may progress at once to the customary finishing steps employed 1n the manufacture of sheet roofing. If the product is to be marketed as saturated felt,it is desirable to regulate the quantity of excess saturant on the surface to such an amount as .will

dry in when the product is cooled and woundv into rolls. Generally, however, the saturated felt is further converted to a coated roofing product, in which case sufficient excess 1s allowed to cover the surface so that during cooling of the sheet air cannot have access to its surface and thereby cannot be sucked into the sheet. On the contrary under these conditions the cooling contraction must result 1n drawing liquid saturant into the pores of the felt. lAs shown on the drawing, the sheet is led to a conventional coating apparatus comprising a. spout 24 through which high melting-point or blown asphalt is supplied to the upper surface of the sheet and spread in a layer of suitable thickness as by a roll 25. A coating of similar .asphalt is applied as by a roll 26 to the under face of the sheet, the asphalt for this coating being picked up from a container 27 as by a feed roll 28. The asphalt used in tanks 17, 2l and 27 is generally identical. In the usual process of coating a saturated sheet, bubbles of entrained air appear on the surface immediately after the coatingstage. These bubbles when afterwards broken, may leave small openings by which Water can enter the saturated felt. By the rocess here described, any such imperfectlons in surface coating on the sheet as it leaves the tank are covered by the second coating applied by rolls and 26. The coating of the final sheet comprises therefore in effect, a double layer or film in whichminor imperfections of either application are covered or eliminated by the other. The coated sheet is then surfaced with comminuted material as desired. This material may comprise crushed slate or equivalent granular mineral for one or both surfaces, or powdered material such as mica or talc may be employed for either or both faces. As shown, a receptacle 29 for powdered talc is provided with a series of brushes 30 by which the talc may be applied to the under face of the sheet in order to make it non-Stic?. The upper face is surfaced with crushe slate or its equivalent y from a hopper 31, a suitable receptacle 32 being provided to catch excess slate whichl may fall from the edge of the sheet. The sheet is thereupon led over a suitable series of cooling rolls 33 after which it is ready to be cut into roofing elements of desired shape or rolled up for shipment as finished sheet roofing.

By saturating the raw felt as ereinbefore described, l obtain a saturated sheet of superior quality which is more durable than roofing of this type as now generally manufactured, the Sheet containing in the body thereof a considerable percentage of high melting-point asphalt which bonds with the coating layers of asphalt and results in the production of roofing of unusual strength and durability. lff a somewhat less thoroughly saturated sheet is deemed suicient, the second immersion in bath 21 can be omitted, but in all cases the sheet emerging from the primary saturating bath 12 is freed from as much-of the low melting-point asphalt as possible by the squeeze rolls and the surfaces are immediately covered with an excess of high melting-point asphalt and subjected to a cooling stage while completely covered with sufficient asphalt to Yreclude access of. air to the sheet' proper. tl should be understood that the cooling stage in all cases must be so regulated as not to chill the asphalt on the surface so rapidly asto render it non-fluid before the suction of the sheet has expended itself in drawing in the maximum amount of liquid on the surface. p The sheet is then subjected to the coating operation as heretofore described. y

Having thus described an embodiment of my invention, it should be evident to those skilled in the art that many changes and modifications may be made therein Without departing from its spiritor scope as defined by the appended claims.'v

I claim: 1. -A methodl of saturating sheet roofing felt, which comprises wetting the fibres with liqueed low melting-point asphalt, applying molten high melting-point asphalt to the surface of the sheety while it is hot, allowing the sheet to cool, immersing the sheet in molten high melting-point asphalt, and allowing the sfheet to cool with excess asphalt on the surace.

2. A method of saturatin sheet roofing felt, which comprises immersing the sheet in a bath of low melting-point asphalt, removing the sheet from the bath, removing excess saturant from the surface of the sheet, applying molten high melting-point asphalt at once to the hot sheet, allowing the coated sheet to cool, immersing the sheet in molten high melting-point asphalt, and allowing'it to cool again. y

3. A method of saturating sheet rooiing felt, which comprises impregnating the body of the felt with hot lo'w melting-point asphalt, removing from the surface of the sheet any excess asphalt thereon covering the surfacev of the hot sheet with molten high melting-A point. asphalt, permitting the saturant within. the sheet to contract and suck highrnelting-point asphalt into'the body of the sheet, immersing the sheet in a bath of molten high melting-point asphalt, removing the sheet from the bath, 'and allowing it to cool.

4.. A method of making sheet roofing, which comprises immersing sheet roofing felt in a bath of molten low melting-pointv asphalt, removing the sheet from the bath, removing excess low melting-point asphalt from the surface of the sheet, applying at once thereto a coating of high melting-point asphalt, allowing the sheet to cool, immersing the sheet in a bath of molten high melting-point asphalt, removing the sheet, allowing cit to cool with excess asphalt on the surface, coating the surface of the cooled sheet with high melting-point asphalt, and surfacing the coating with comminuted material.

5. The method' of making sheet roofing, f

which comprises immersing a sheet of felt in a bath of molten low melting-point asphalt,-

removing the sheet from the bath, supplying A 'further quantities of liquefied asphalt to the surface of the sheet, cooling said sheet with T excess asphalt on the surface thereof, and thereafter coating the surface of the sheet with high melting-point asphalt.

6. The method of making sheet roofing, which comprises immersing a sheet of. felt in a bath of molten low meltmg-point asphalt,

removing excess asphalt from the surface` in aV bath of molten low-meltin -point asphalt, removing the sheet from sai bath, applying to the surface of the sheet liquefied asphalt at a temperature lower than that of the sheet at the point of application, permitting the sheet to cool with excess asphalt on the surface thereof, and thereafter coating thev surface of the sheet with liquid high melting-point as halt.

In testlmony W ereof I have affixed my signature.

LESTER KIRSCHBRAUN. 

